Mechano-chemistry of rock materials for the industrial production of new geopolymeric cements

The reduction of CO emission from cement industry represents a priority task in the roadmap defined for the year 2020 by the European Union (EU) Commission for a resource efficient Europe. Several research projects have been undertaken aimed at developing non-hazardous materials as partial substitute of clinker in cement formulations, but also new, low-carbon, cements fully replacing clinker. Among the new cementing materials, Si-Al geopolymers seem the most promising, in terms of CO emission and mechanical and thermal properties. In this chapter, mechanochemical processing of kaolin clays to produce metakaolin (MKA) for the synthesis of Si-Al geopolymers is proposed as an alternative process to replace thermal treatments performed at 650-850 °C. Results obtained show that the mechano-chemical process is also suitable to make low cost blended Si-Al geopolymers where 40% of MKA is replaced by mechano-chemically activated volcanic tuffs. The compatibility of mechano-chemistry with industrial production was investigated by building a prototype milling system that was tested in a small industrial facility producing zeolites from industrial wastes. The degree of automation allowed the prototype to work unattended for 10 months. Based on the results obtained from these tests, a milling system for a full scale production of mechano-chemically activated rock materials was designed, and its performances analysed.